HANS PETER HERZIG, IWAN MÄRKI, TORALF SCHARF,
AND WATARU NAKAGAWA
iffractive optical elements are components that rely on the physical phenomena of diffraction and interference to control the propagation of light. 1, 2, 3 Such elements are usually macroscopi-
cally planar microstructures, consisting of features with dimensions from a couple of wavelengths to a few tens of microns and are designed by advanced numerical algorithms based on diffraction theory. They are fabricated by modern micromachining, including optical lithography, direct-laser and electron-beam writing, and reactive-ion etching.
In the past decade, diffractive optics has emerged as a powerful tool to realize various optical functions that have not previously been possible or feasible using conventional optical elements. In parallel, microlens technology has been developed based on the same fabrication technologies that enable efficient batch fabrication. Such elements, using either refractive or diffractive surfaces, are now found in applications ranging from laser-beam shaping in laser-based materials processing to optical in-terconnects in telecom applications.
UNIVERSI T Y OF NEUCHÂTEL
FIGURE 1. A miniaturized Fourier-transform spectrometer is based on a tunable grating.
One of the major strengths of micro-optics compared
to conventional optics lies in the fact that micro-optics
allows integration of large, complex optical systems into
much more compact form. In addition, emergence of rep-
lication techniques such
From diffractive optics as injection molding al-
at the microscale to low the low-cost mass- production of micro-
plasmonics at the nanoscale, optical elements. One
example is a compact
microstructures have unique heart of this spectrometer is a tunable grating
and valuable properties. with variable depth (sev-
eral hundred microme-
ters) realized by silicon micromachining. 4
The progress in diffractive optics, or micro-optics in general, is closely related to the progress in microfabrication technology. In addition, powerful computers are now available to efficiently calculate complex optical structures based on Maxwell’s equations. As a result, researchers working in diffraction optics are now increasingly working with structures containing subwavelength-size features.
HANS PETER HERZIG is a full professor, IWAN MÄRKI is a postdoctoral researcher, TORALF SCHARF is a group leader and lecturer, and WATARU NAKAGAWA is a group leader at the Institute of Microtech-nology, University of Neuchâtel, A.-L. Breguet 2, 2000 Neuchâtel, Switzerland; e-mail: HansPeter.Herzig@unine.ch.
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